Deodorization of gasoline is one of the indispensable technical processes in petrochemical industry in order to remove the organic sulfides with malodor or transform the sulfides to odorless substances. With the exploitation of petroleum, the reserves of petroleum on earth becomes less and less. In recent years, as densification and inferiority of the crude oil, and improvement of the depth of processing for crude oil, the content of mercaptans and thioethers with more complex structures in gasoline from refinery factory becomes increasingly high. This leads to deodorization of gasoline becoming more difficult. Therefore, many refineries all over the world do their endeavor to develop new technologies to improve the efficiency of deodorization.
Mercaptans have the most harmful effect on the quality of gasoline, wherein mercaptans present in FCC (Fluid Catalytic Cracking) gasoline, thermal cracking gasoline, coker gasoline, and straight run gasoline result in the malodor of the gasoline product, since mercaptans are initiators of free radical, making the quality and stability of gasoline being decreased; and mercaptans themselves also have corrosiveness, causing the corrosion of the engine parts. Accordingly, it is necessary for gasoline to be deodorized in order to satisfy the requirements of production need and environmental protection.
At present, deodorization technology being widely used in industry is an alkali-free deodorization technology, which feature is that a feedstock oil and an activator solution are mixed completely by a mixer, followed by reacting with air when they are passed through the catalyst bed together with the air. The removal efficiency of mercaptans is relatively high, and the amount of sodium hydroxide used is decreased considerably.
Chinese Patent No. CN1248609A discloses a preparation method of a fixed bed catalyst impregnation solution, comprising: adding a phthalocyanine cobalt compound into a 0.5-2% of an aqueous solution of alkaline metal oxide (wherein the alkaline metal is referred to as potassium, sodium). Because the solution is strongly basic, the phthalocyanine cobalt compound could transform into the non-reactive component, leading to concentration of the active phthalocyanine cobalt compound in the impregnation solution being decreased.
U.S. Pat. No. 4,913,802 discloses a preparation method of an impregnation solution, comprising: adding a cobalt phthalocyanine into an aqueous mixed solution of 2% of ammonia and 1% of a quaternary ammonium base. Although the transformation from the cobalt phthalocyanine to non-reactive component is slowed down; the fixed bed catalyst prepared with the impregnation solution is prone to be leached during the deodorization, resulting in not only causing unfriendly a pollution on the environment, but also reducing the life time of the fixed-bed catalyst.
Chinese Patent No. CN101063042A discloses a method of desulfurization and deodorization via oxidation, comprising: taking heteropoly acids and heteropoly acid salts as homogeneous catalyst, and carrying out a reaction in highly effective mass transfer reactor with an internal strengthened swirling component to get the high-quality oil product with low-sulfur and no odor. However, it is too difficult for the method to recycle and reuse the homogeneous catalyst.